Facebook said it is pushing deeper into the mobile business while shooting down reports that it is building its own smartphone.

“Facebook is not building a phone,” a company spokesman said. “Our approach has always been to make all phones and apps more social.”

“Our view is that almost all experiences would be better if they are social,” he added. “Integrating deeply into existing platforms and operating systems is a good way to enable this.”

Facebook cited several examples of this approach, including a phone made by INQ, a Hong Kong-based handset manufacturer, that revolves around Facebook integration.

The INQ1, which Facebook said is sometimes referred to as “the Facebook Phone,” also emphasizes services such as Ebay, MySpace and Skype among others.

Facebook was responding to a TechCrunch report on Sunday that said the social-networking site was secretly working on a phone and had hired key executives for the project.

Analysts who cover the mobile space expressed doubts that Facebook is building a phone, but said the site — with some 500 million users — can certainly benefit from advancing its mobile businesses.

ComScore mobile analyst Mark Donovan said the company has seen social networking on phones explode, doubling over the past year. He said 150 million people a month are using phones to access social-networking sites.

“It’s growing at a faster rate than the mobile Web audience,” he said. “It’s a stand-out.”

But Donovan said it doesn’t make a lot of sense for Facebook to come out with a phone.

“It’s an increasingly competitive space in terms of the operating system world,” he said. “It would be off point for their business.”

Facebook has partnerships with phone providers across several operating systems and provides a stripped down service to mobile partners, called Facebook Zero, which omits video and pictures to save on bandwidth.

S&P’s tech analyst Scott Kessler cast doubt on the notion that Facebook might simply slap its brand name on a phone service made by someone else.

“I’m really skeptical about that,” he said. “They’ve made a fair number of errors, and they need to be careful about the brand.

“They fully realize there are a lot of exciting licensing and branding opportunities, but they are being careful about how to proceed.”

Meanwhile, Facebook is an ad-supported business and rivals Google and Apple have already acquired mobile ad networks.

Facebook is adding geographic and contextual targeting to its services in order to offer advertisers something unique.

Owning a piece of a mobile phone operating system might give it further insight into how and where consumers are using Facebook’s services.

“Mobile advertising is growing,” Kessler said. “What we’re seeing with mobile ads is a lot of continued growth.”

Research firm eMarketer predicts that mobile ad spending will reach $187 million in 2010.